Electron beam discharge device



300'. EZECTRODE N0. 3 1 01/29 2 Sheets-Sheet 1 NO. I VOLTS=.90 [V0.2 VOLTS= 720 No.4 VOLTS= 70 M25 VOLT$= 22 40,000 OHMS INPUT Efim idi H. C. THOMPSON ELECTRON BEAM DISCHARGE DEVICE Filed 00L 1, 1938 V OL U M E CONTROL V01 TA 65 Aug. 26, 1941.-

INV EN TOR. HARRY C. THOMPSON %wwwr A TTORN E Y.

Aug. 26, 1941. C THOMPSON 2,254,096

, I ELECTRON BEAM DISCHARGE DEVICE Filed Oct. 1, 19-38 2 Sheets-Sheet 2 OSCILLATOR l I I H 2 .*44 I i y-Ol/TPUT /NPUT mm :l/OLZ/ME .4 kw: i Hr- -'rl I I s .L ;'/9 nun! i mm 2 lll 1/ f mm 304mm 27 25 /oz/rpur INVENTOR. HARRY c'. THOMPSO/V w zu l A TTORNEY.

Patented Aug. 26, 1941 ELECTRON BEAM mscnAaGEpEvIoE Harry 0. Thompson, Newark, N. J., assignor, by

mesne assignments,

to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application October 1, 1938, Serial N0. 232,805

14 Claims.

5, 1935 and assigned to the same assignee as the present application.

One object of my invention is to provide electron discharge devices of the beam type which are efllcient and utilize substantially all of the emission from a thermionic cathode and in which the total discharge from the. cathode is formed into one or more of more or less well defined beams which are utilized in novel and effective ways toobtain improved tubes having advantages unobtainable with the conventional types of tube structure.

Another object of my invention is to provide improved electron discharge devices which are of much the same dimensions and are operated at much the same voltages as the conventional receiving tubes and in which various desirable characteristics are obtained by segregating the space current into an electron beam or beams and utilizing the properties of the beam to advantage.

Still another object of my invention is to provide efllcient electron discharge devices having desirable transconductance and impedance characteristics which are not obtainable with the conventional type of tube structure.

Another object is to provide an improved neg-' ative resistance electron discharge device in which the negative transconductance or negatlve resistance is substantially constant, is independent in magnitude of the external circuit constants, and is not dependent upon secondary emission or space charge effects.

Still another object is to provide improved means for rendering the distribution of the electron stream in space. nonuniform and for forming the electron stream into electron beams.

Again in so-called mixer or converter tubes particularly suitable for use in superheterodyne circuits, a stream of electrons emerging from a cathode is usually directed through a plurality of grids to an anode, two of which grids are control grids for influencing the electron stream on its way to the anode. Such a tube may be used as a mixer tube in which input oscillations are supplied to one of the control grids and local oscillations produced by the local .oscillator to the other of the two control grids. The tube may also be used as a self-oscillating mixer tube or so-called converter in which the local oscillations are produced between two grids or electrodes of the tube itself.

At frequencies higher than broadcast the output'of the present detector oscillator is lower than. the calculated value. This is probably caused by the electron coupling of the oscillator to the signal grid in adverse phase relation by virtue of the existence close to the signal grid of a virtual cathode modulated by an oscillator as explained above. It is believed that this adverse action is inseparable from the device act- 115g on the principle of a modulated virtual catho e.

Hence it is another principal and more specific object of my invention to provide an improved electron discharge device particularly suitable for use as a mixer or converter tube in radio circui and making use of controlled beams at low vol ges.

I electron discharge devices, made according to the present invention the undesirable characteristics of conventional tubes as'noted above are avoided. In one form of tube having a double control and made according to my invention the 30 electrons emanating from the cathode are supplied in the form of beams and along curved paths through a control and screen electrode arranged in the immediate vicinity of the cathode.

One control occurs on the control grid arranged 35 in the immediate vicinity, whereas the other control occurs in that part of the space from which the electrons can substantially not return to the first-mentioned electrodes, thereby curing one of the defects of conventional mixer tubes. The 40 paths over which the electrons are influenced by the voltages applied to this second control electrode are longer than the paths over which they are influenced by the first control electrode.

When the electrons-are directed in the formof beams along curved paths it is possible to effect the second control at such a point of the space charge that the electrons substantially cannot return to the vicinityof'the first control grid, and it is possible, without rendering the construction of the tube too complicated or its size too large, to give the paths such a length that the electrons can be controlled also by electrodes having a lower alternating voltage applied to 55 them. It is found that by such a construction the current to the first control grid can almost entirely be suppressed. and that the input damping of such a tube is very much reduced. This is particularly desirable when the tube is used as a mixer tube or as a converter.

The novel features which I believe to be char-- acteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken inconnection with the accompanying drawing in which Figure 1 discloses an electron discharge device made according to my invention and disclosed in the above identified co-pending application, Figure 2 is a graph showing the characteristics of the tube shown in Figure l, and Figures 3, 4 and 5 are transverse sections of modifications of electron discharge devices made according to my invention and their associated circuits.

An electron discharge device made according to my invention is provided with a straight thermionic indirectly heated cathode having disposed on opposite sides a pair of focusing rods l2, these rods being labeled No. 1. The screen or shield No. 2 partially surrounds the rods and is provided with a pair of slots which form oppositely disposed electron beams, one of such beams being indicated by the dotted lines. Adjacent the screen or shield is a negative transconductance or work electrode l4 indicated as electrode No. 3, the output electrode or rejector electrode I5 being positioned adjacent electrode No. 3 and 180 away from the cathode ll. Surrounding all the other electrodes is the electrode |6 to which is supplied a low positive, zero or low negative potential with respect to the cathode, positive voltages being applied to the No. 3 and 4 grids. The electrons composing the beam are diverted after leaving the opening in electrodes No. 2 into arcuate paths, as indicated, causing them to arrive on No. 3 or the more remote electrode No. 4. At a certain potential of No. 3 electrode, the beam will impinge upon parts of No. 3 close to the cathode and at a higher potential on No. 3 will impinge on parts more removed from the cathode and at still higher voltages the beam will miss No. 3 and arrive at No. 4 as indicated by the outermost dotted line. Thus a sufllcient rise of potential on No. 3 electrode causes the current to No. 3 to fall substantially to zero by being diverted to No. 4 electrode. Figure 2 shows characteristic curves of this device with the critical potential on No. 3 at 120 volts positive, the succeeding falling of No. 3 characteristic occurring while the potential on No. 3 becomes higher than that of any other electrode in the device. The corresponding and simultaneous rise of the current diverted to the No. 4 electrode is also shown in Figure 2.. The beam behavior in the device of Figure 1, which gives rise to the negative transconductance of the No. 3 electrode, is due to the efiect that the rise of potential on No. 3 has in lengthening the trajectory of the electrons emerging from the slits in the No. 2 electrode. The behavior of the beam traces on the No. 3 and 4 electrodes and the beam paths observed when gas is present in this device correspond to the above explanation.

,I have found that the electrode No. 3 may be cylindrical so that the field of electric force between it and No. 5 is substantially radial except near the No. 2 and No. 4 electrodes. Such constructions are shown below.

In Figure 3 is shown an electron discharge device made according to my invention and used as a converter tube in superheterodyne circuits.

In this form which has an envelope 20 the oathode 2| is surrounded by the control grid having beam forming shields 22 and solid shield grid 23 provided with oppositely disposed slots for forming oppositely disposed electron beams. A pair of coaxial cylindrical electrodes 24 and 25 have the cathode 2| and electrodes 22 and 23 positioned therebetween. The output electrode 26 which has positioned around it the shield member 21 'is provided with oppositely disposed slots. The output circuit 30 is connected between output electrode 26 and the positive source of voltage I9. The input circuit 28 is connected between the cathode 2| and the control grid 22 and the oscillator between the inner tubular member 25 and the source of voltage supply IS. A volume control circuit may be connected between the cathode 2| and the external cylindrical electrode 24. In this arrangement the electron beam is modulated by the signal impressed through the input circuit. A varying voltage is applied to the inner electrode 25 by the local oscillatorcircuit and causes the electron beam to impinge either on the electrode 25, shield electrode 21 or output electrode 26.

The voltage applied to the outer electrode 24 from the volume control circuit shifts the'position of the beam so as to increase or decrease the amount of current flowing to the output electrode for the same voltage conditions of the oscillator.

In Figure 4 I show a modification of the tube shown in Figure 3. Here the cathode 3| surrounded by control grid 32 and beam forming shield grid 33 are positioned between concentric coaxial cylindrical electrodes 35 and 36, theelectrode 36 being provided with apertured vanes 31, the output electrode 38 being positioned between the vanes and spaced away from the cathode. The oscillator voltage instead of being applied to the internal cylindrical electrode 36 is applied to a grid electrode 39, the shifting of the beam being controlled by means of this control grid, the electrodes 35 and 36 merely forming the proper field for causing the beam to make a curved path. The input circuit 4| is connected between the cathode 3| and control grid 32, the oscillator circuit 42 between the control grid and the cathode 3| and the output circuit being connectedbetween output an'ode 36 and the positive side of the voltage source 44.

In Figure 5 I show a still further modification -of an electron discharge device made according to my invention. In addition to the electrodes shown in the construction shown in Figure 3, I provide an auxiliary cathode 50 and control electrode 5| inside and coaxial with cylindrical electrode 25. The cathode 50, grid 5| and cylindrical electrode 25 form the oscillator section of the tube which is completely screened from the remainder of the tube, thus preventing interaction between the input and the oscillator sections. The input circuiti26 is again connected between the cathode 2| and the control grid 22, the oscillator circuit 29' being. connected between the electrode 25 and the positive source of voltage.

Feedback to the grid 5|.is obtained by means electrons from the plane of the shield in Figures3, 4 and-osurrounding'the output electrode to the "effective arrival at the output electrode.

' Thetransit tim'e betweenthe No. 2 or first shield and-the shield around the output electrode has no adverse effect. The volume control. electrode is disassociated from the input electrode. .The shielding of the .input electrode from the oscillator isgood and can be made asgreat-as desired.

No virtual cathodeis used. There is an inherent tendency in the double beam structure as disclosed here .ior .the efiect of a stray magnetic v field 'on onebeam to becanceiedbya necessarily reverse eiiect on the other beam. This isa new and important characteristic in avoiding difliculties due to straymagnetic fields. The characteristics or output electrodesmay be made to approximate those of aipentode structure without the use of suppressor since the shape of this electrode greatly reduces secondary .emission from it.

While I have indicated the preferred embodiments of my invention oi which I am now aware and have also indicated only one specific application ior which my invention may be=employed, it will be apparent that my'invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure usedand the purpose for which it is employed withoutdeparting 'from the scope :otmy invention asset for-thin the appended claims.

What I claim as new is: '1. An electron discharge device having an envelope containing a cathode, a first control grid surrounding said cathode and means adjacent said first control grid and said cathode. for providing -a pair of oppositely directed beams of electrons from said 'cathode,"means in the path of 'saidoppositely disposed beams of electrons for causing said beams to travel curved paths and including a second control electrode, an anode for intercepting the beams and'an auxiliary electrode adjacent said anode,.:said second controlelectrode adjacent the path of "the beams being adapted to shift the beams between the anode-andauxiliary electrode to varythe output from said anode during operation of the device.

2. An electron discharge device having an envelope enclosing a cathode, a control grid and soreen electrode surrounding said cathode for providing a pair of oppositely directed beams from said cathode, a first cylindrical electrode surrounding said grid and cathode, and a second cylindrical electrode coaxial with and inside the first cylindrical electrode,'said cathode and grid being positioned between said cylindrical electrodes, and an output electrode positioned between said cylindrical'electrodes 180 removed from said cathode.

4. An electron discharge device having a pair of concentric coaxial cylindrical electrodes, a.

cathode and a control grid surrounding said electrode adjacent and inside said outer cylincathode positioned between said cylindrical 'electrodes, and an output electrode positioned between said cylindrical' electrode .-180:'removed .irom :sai'd :cathodeand controligrid.

5. .An electron "discharge device having a pair of :concentric coaxial cylindrical electrodes, a ca-thodeand a control grid surrounding saidcathode and a solid-shield beamiiormingcscreentelectrode surrounding said cathode :and control grid -positioned between said cylindrical electrodes,

and an output electrode'positioned between said cylindrical electrode 180" removed from said cathode and control grid.

6. An electron dischargedevice having a pair of concentric coaxial cylindrical electrodes, a cathode and a control grid surrounding said cathode and a solid shield-beamiormingscreen electrode surrounding said cathode and control grid positioned between said cylindrical electrodes, and .an output electrode positioned between said cylin'dricaljelectrodes 180 removed .from said cathode-and control grid, and a solid electrode'provided with an aperture surrounding said output electrode.

7. An electron discharge device having a pair of concentric coaxial cylindrical electrodes, a cathode and. a control grid surrounding said cathode positioned between said cylindricalelectrodes, and an outputelectrode positioned between said cylindrical electrode .180 removed.

irom'said cathodeand control grid, anda Jgrid drical electrode and surrounding said other elec- .trodesf 18. An electron discharge device including an I enveiope containing a pair of concentric cylindrical electrodes, a-=.;grid-like control electrode positioned adjacent and inside 'the outer cylindricalelectrode; 1a cathod'eand control grid positionedbetween said-grid electrode and said inner cylindrical electrode and abeamiorming .screenelectrode surrounding said grid and cathode, and an output-electrode positioned between said control grid electrode and said inner cylindrical electrode ,and positioned 180 from said cathode and control grid.

9. An electron discharge device'comprising an envelope containing a pair of coaxial concentric cylindrical electrodes, a cathode and a control grid surrounded by :said cathode positioned between saidcylindrical electrodes, and-an output electrode positioned between said cylindrical electrodes and removed .180 from .said cathode and control ggrid, -and=a cathode and control electrode positioned within said inner cylindrical electrode.

and ax-cathode and control grid positioned with-.

10. electron discharge device comprising an envelope containing a pair. of coaxial concentric cylindrical electrodes, a cathode'and .a control grid surrounded .by'said cathode and a beam forming shield electrode surrounding said first cathode and control grid positioned between said cylindrical electrodes, and anoutput electrode positioned between said cylindrical electrodes and removed from said cathodeand control grid,

in said'inner cylindrical electrode, and a solid shield electrode provided with an aperture surrounding said output electrode.

11. An electron discharge device having an envelope containing a' cathode, a first control grid surrounding said cathodeand means adjacent said cathode and first control electrode forproviding a pair of oppositely directedbeams of electrons from said cathode, means in the path oi said oppositely directed beams of electrons for causing said beams to travel curved paths toward each other and including a second control electrode positioned between the curved paths of said beams, an anode for intercepting said beams and an auxiliary electrode adjacent said anode, said second control electrode being adapted to shift said beams alternately toward and away from each other and between said anodes and auxiliary electrode to vary the output from said anode during operation of the device.

12. A negative conductance electron discharge device comprising means for segregating an electron discharge into a beam, a work electrode and a rejector electrode out of alignment with the initial path of said beam, and means including an electrode enclosing said means and said other electrodes for causing said beam to follow arcuate paths to either of said electrodes at will.

13. An electron discharge device comprising beam forming means for segregating an electron discharge into a pair of oppositely directed beams, a pair of current collecting electrodes out of alignment with the initial paths of said beams and at diflerent distances from said beam forming means, and means including a curved sheet electrode enclosing said beam forming means and said electrodes for causing said beams to follow arcuate paths and to change the radius of curvature of said paths at will.

14. An electron discharge device having an envelope enclosing a cathode for supplying electrons, means adjacent said cathode for form- 'ing the electrons into a directed beam, means including a curved sheet electrode in the path oi said directed beam for causing said beam to follow a curved path and a control electrode adjacent the curved path of said beam for changing the radius of curvature oi. said path and an anode in said curved path for intercepting said beam.

HARRY C. THOMPSON. 

